Method for making twisted flexible wave guides



July 1957 D. INGALLS ETAL ,00,705

METHOD FOR MAKING TWISTED FLEXIBLE WAVE GQIDES Original Filed April 8. 1950 2 Shee'ts-sheet 1 '1 HM. HI H IIHHII IIHIHH David [ugalls By Jean Milan lion T e IV. finderson HTIWRNEY y 1957 D. INGALLS ETAL 2,800,705

METHOD won mmc *rwzsmn msxzsns: WAVE cums Original Filed April 8, 1950' 2 Sheets-Sheet 2 N David Inga-1Z8. BY Jean M Hamilton Tore If llnders'on arronms'r METHOD FOR MAKING TWISTED FLEXIBLE WAVE GUIDES David llngalls, Mountainside, Jean W. Hamilton, Montclair, and Tore N. Anderson, Mountainside, N. J., assignorsto Airtron, Inc., Linden, N. J., a corporation of New Jersey Original application April 8, 1950, Serial No. 154,796. Divided and this application October 8, 1952, Serial No. 313,744

7 Claims. c1. 29-4555 This application is a division of copending application filed by us under date of April 8, 1950, and under Serial No. 154,796, now abandoned, and is being filed pursuant to a requirement for division made by the examiner and sustained by the examiner of classification during the prosecution of said application.

This invention relates to novel methods for making flexible wave guides such as are employed to transmit microwaves between various components of radar apparatus and television or other electrical equipment.

Wave guides have been made flexible principally to enable them to be bent to facilitate their installation in the equipment of which they form an electrical impulse conducting part. One form of flexible wave guide, which has been found in practice to be highly eflicient conductively'and in other respects, includes a conducting core of generally rectangular cross-section which is formed by winding thin, strip, conducting metal spirally on a rectangular mandrel, the strip being ridged longitudinally to form transversely extending convolutions in the core so that it may be bent to facilitate its installa tion. The edges of the strip are soldered to enhance the conductivity of the wave guide, but this limits the flexing of the wave guide to bending thereof and excludes the possibility of twisting it. Such wave guides are usually made in straight or untwisted form, but in some installations a twisted Wave guide may be very useful in establishing a desired connection. 1

An important object of the present invention is the provision of simple and efiective methods by which such twisted, flexible wave guides may be manufactured.

The foregoing and other objects are accomplished by the present invention which, for illustrative purposes, is shown in some particularity in the accompanying drawings without, however, limiting the invention to such particular illustrated structures.

In the drawings:

Figure 1 is a side elevation of a twisted flexible wave guide, manufactured according to the present invention, one end of the wave guide being cutaway to show a portion of it in transverse section.

Fig. 2 is a greatly enlarged fragmentary view of the upper portion of the wave guide shown in section in Fig. 1.

Fig. 3 is a perspective view of apparatus, according to this invention, for converting a non-twisted wave guide into the form of a twisted Wave guide; this apparatus also being suitable for practicing the method hereinafter described as a part of the present invention.

Fig. 4 is a vertical sectional view of the waveguide twisting apparatus on the line 4-4 of Fig. 3.

Fig. 5 is a top plan view of the right end of the apparatus shown in Fig. 3.

Wave-guide twisting apparatus according to the present invention may be of various designs, but Figs. 3-5, inclusive, of the drawings illustrate a preferred embodiment of twisting apparatus within the invention.

nited States Patent Patented July 30, 1957 In the illustrative embodiment shown in the drawings, a rectangular base plate 11 has a metal end plate 12 fixed upon one end thereof in upright position by any suitable means, as, for example, by an angle bracket 13; and the plate 12 is connected by an electrically conductive cable 14 in a relatively low voltage electric circuit of high amperage.

Toward the other end of the base plate a metal, rotatable end plate 15 is mounted thereon in a vertical position extending in a plane parallel to the plane of the opposite end plate 12. The plate 15 has a coaxial cylindrical extension 16 fixed at its outer end and the said extension, in turn, has fixed thereto a coaxial shaft 17 extending horizontally through a bearing 18 whereby to be supported in the latter for rotation. The shaft 17 is provided at its outer end with a handle which may be in the form of an operating lever 19 by which the shaft and its integrally associated parts, particularly the plate 15, may be rotated. Y

The bearing 18 is supported upon a block 20 of suitable insulating material, as, for example, Micarta or the like. The block 20 restsrupon the top of the base plate 11, and the bearing 18 and said block arefastened down upon the base plate by headed bolts 21 which, by means of insulating washers 22 and cylindrical insulating sleeves 23, are effectively insulated from the bearing 18. The bolts 21 extend downwardly through suitable bolt holes in mounting lugs 18a of the bearing, and in the block 20, thence through longitudinal slots 24 formed in the base plate 11 and through suitable bolt holes in a clamping crosspiece25 engaging the underside of the base plate 11; and Washers 26 and nuts 27, the latter of which are threaded onto the lower ends of the bolts 21, serve to hold the several mentioned parts in assembled relation upon the base plate. The nuts 27 may advantageously be square and seat witihn elongate bot tom recesses 25a in the crosspiece 25; the said recesses, preferably, being narrower than the diagonal dimension of the nuts 27 and wider than the latters side-to-side dimension so that the nuts cannot turn materially in said recesses. Y

Byloosening the bolte 21, the block 20 and the rotatable plate assembly which it carries may be shifted longitudinally of thebase plate 11 so that the apparatus can be adjusted for twisting wave guides of different lengths.

A flexible, electrically conductive cable 28 is suitably bolted at its connecting lug 28a to the end plate 15, and serves as a means of connecting the latter in the previously mentioned low voltage-high amperage electrical circuit. As the plate 15, in normal operation of the device, need never be rotated more than approximately the cable 28 preferably is sufliciently flexible and possessed of suflicient freedom of movement as not to materially oppose rotation of the plate 15. In addition, the lug 28a may be pivotally connected to the plate 15, if desired, thereby enhancing the freedom of rotation of the latter.

As best seen in Fig. 4, the plate 15 is provided with plural sets 29, 29a and 29b of threaded holes to enable Wave-guide connection flanges of various sizes and bolthole arrangements to be bolted to said plate. Although the opposed side of plate 12 is not visible, nevertheless, that side of plate 12 is similarly provided with plural sets of such threaded holes. Also, although not an essential feature of the invention, the plate 15 may advantageously be provided with graduation marks 30 with suitable indicia applied thereto indicating up to about 95 rotation of the plate; and a pointer 31, suitably fixed to the block 20, may have an indicating portion thereof overlying the graduation marks 30.

Another advantageous feature of this device, but one which, nevertheless, may be omitted while still utilizing a substantial phase of the present inventive concept, re-

by a flange-33 to theplate 12 in-alignmentwitha bore-34 in the latter through which compressedair maybe introduced from said pipe onto the interior of a wave guide bolted to the plate 12. As best seen from Figs. 4 and 5, the plate 15 may also be formed with a bore-3'5 which extends coaxially through the plate 15 and into the cylindrical extension 16; and an open radial bore 36, formed in the latter and communicating at its inner end with the bore 35, may be provided toserve as a discharge passage for carrying off, to free air, the compressed air introduced into the wave guide forcooling purposes. If a liquid, such as water, is used as a cooling medium, suitable flexible piping or tubing shouldbe connected to the discharge end of the bore 36 to carry off the liquid to a suitable container or to waste.

Although the apparatus hereinbefore describedis suitable for twisting wave guides of various types, nevertheless, one type of wave guide which may be twisted by this machine is illustrated in Figs. 1, 2 and 3 of the drawings. The wave guide includes a flexible, electrically-conductive core 37 which is formed by winding longitudinally-grooved, thin, flexible metal strip, upon a mandrel of rectangular cross-section, in such fashion that adjacent edges of successive turns of the strip material enter into interlocking relationship as at 37:: and are rolled down at such interlocking edges as the strip is spirally wound upon the mandrel; and the mentioned longitudinal grooves are such that the metal core is spirally convoluted as indicated at 38. As the strip material is wound upon the mandrel to form the core, a thread of solder and suitable soldering flux is also wound with the strip and melted so that the spiral seam joining adjacent turns of the strip includes such bonding solder as at 39, as a means of sealing and strengthening the seam and enhancing the electrical conductivity of the core. Because of the fact that the core is of thin material and is convoluted as described, it may be bent, but because the spiral seam is soldered, the core cannot be twisted. i As s'uch'flexible wave guides may be most economically made in'straight or untwisted form, a wave guide is first made with a straight or untwisted core 37. Connecting flanges 40 preferably are soldered upon the ends of the core as at 42, the solder preferably extending completely around the core in order to provide an air-tight connection between the core and the flanges. Then, a jacket 43 of flexible rubber, synthetic rubber, or other suitable moldable rubber-like material, is molded upon the core to completely envelop the latter and to extend into a firm bonding engagement with axial extensions 44 of the flanges 40. The flanges 40, and particularly their extensions 44, are preferably treated with a suitable bonding composition such as bonding rubber or other suitable adhesive, or the flange and its extension may be otherwise treated for the purpose of assuring a firm bonding of the jacket material with the flanges 40 and their extensions 44. It has been found advantageous also to form the extension 44 with an outer peripheral groove 45 and/or an inner peripheral groove 46, into which groove or grooves the jacket material will flow and become firmly bonded during its molding to form air-tight connections thereat between the flanges and the jacket.

When the wave guide is made with the expectation that it may carry air therein under considerable pressure to enhance its conductive qualities, some or all of the convolutions of the core 37 may have apertures 47 formed therein so that the compressed air will not deform the core by bulging it outwardly, but instead the air will find its way through the openings 47 to the area between. the

core and the jacket 43 so that the air pressure imposed upon the inner surface of the core will be substantlally balanced by the pressure of the air on the outer surface thereof. Under this arrangement, the jacket 43 functions as the means for containing the air pressure.

Let us now assume that we have a flexible wave guide of the character just described in its untwisted form, in which the solder 39 has previously been heated and then permitted to cool to effect soldering of the core in the manner already described, and that it is desired to twist that wave guide so that the opposite end flanges 40 thereof are disposed at an angle of about relatively to each other when the wave guide is in its unfiexed or unbent condition. In order to use the described apparatus for such twisting, the bolts 21 are loosened, permitting the block 20 with all the structure which it supports to be adjusted along the slots 24 to such a position that the opposing faces of the plates 12 and 15 are spaced apart preferably slightly more than the normal length of the wave guide tobe twisted. The block 20 is then locked in its mentioned adjusted position by tightening the bolts 21.

The untwisted wave guide is then fastened in place by bolting one end flange 40 to the inner face of plate 12 and its other flange 40 to the inner face of plate 15; This is accomplished by the use of machine bolts 4011 or equivalent bolts, pegs, studs orthe like, which may he passed through bolt holes 41 in the flanges 40 and threaded into thethreaded holes 29, constituting a set of such holes which correspond to the holes 41 in the flanges of the wave guide. The tightening of the machine bolts 40a will have the effect ofslightly stretching the wave guide. After 'thewave guide has thus been fastened to the plates 12 and 15, the electric circuit, including the cables 14 and 28 and the plates 12 and 15 and now including the core. 37 of the wave guide, is closed by suitable switch means (not shown), thereby establishing an electric potential between the plates 12 and 15 of about five or six volts and a current-flow through the core 37 which should be. of about to 200 amperes if the wave guide is of relatively small cross-section or of considerably greater amperage if the wave guide is of relatively large crosssection. Upon closing of the described electric circuit, the operator may manually urge, but not force, the handle 19 in a direction (indicated by directional arrows) which would cause twisting. of the wave guide such as would tend slightly to unwind the several convolutions of its core.

The twisting, however, cannot take place until the solder 39 at the spiral seam of the core becomes softened after a relatively short duration of flow of the electric current. As soon as such softening occurs, the handle 19 will yield to the pressure being applied thereto by the operator, whereupon the operator further manipulates the handle to rotate the plate 15 to an extent several degrees greater than the twist desired to be imposed upon the wave guide. In this manipulation, the operator may be guided by the position of the graduation marks 30 in relation to the pointer 31.

As soon as the softening of the solder takes place, also, the operator opens the described electric circuit, but the heat generated by the electric circuit through the core 37 is sustained for a sufiicient time to permit completion of the twisting of the wave guide. After the desired twist has been given to the wave guide, the operator holds the handle 19 in its turned position, to hold the twist until the solder has cooled sufliciently to reharden within the spiral seam of the core and thereby render the twist permanent.

The rubber or rubber-like jacket material may possibly be more or less harmed if the solder. softening heat is sustained for too long. a period of time, although, ordi-' narily, the danger of this is not very great and the harm would not be serious. Nevertheless, to avoid this danger and assure a high quality product, it may be of some advantage for the operator to introduce a quenching or cooling medium such as compressed air into the interior of the wave guide by opening a suitable valve (not shown) in the pipe or tubing 32 as soon as the wave guide has been given its desired twist. The radial bore 36 and possibly also the bore 35 may preferably be of smaller diameter than the bore 34, thus offering some resistance to the passage of air from the interior of the wave guide during the cooling part of the process. The compressed air accelerates the rehardening of the solder and shortens the period during which the heat is maintained in the core 37, thereby speeding up the operation of the apparatus and minimizing the possibility of damage to the jacket 43.

The operator, while holding the handle 19 in the position to which it has been rotated to give the wave guide the desired twist, can know when the solder has rehardened by noting when the handle no longer reflects any tendency of the wave guide to return to its untwisted condition. After rehardening of the solder has occurred, the handle 19 may be released and the machine bolts 40:; removed, whereafter the wave guide in its permanently twisted form may be removed from the device. Then, the handle 19 may be turned back to bring the zero graduation mark on the plate 15 back into register with the pointer 31. In this position of the plate 15, the several sets of threaded holes 29, 29a, 29b therein are directly opposite to corresponding holes in plate 12, so that the two said plates are positioned to receive another straight wave guide for twisting.

It will be perceived that, when the core 37 is heated interiorly for softening the solder by means such as, for example, the electrical heating means hereinbefore de-. scribed, it is entirely feasible to employ the described means for quenching or cooling the wave guide. In contrast, it obvious means such as an oven arrangement were employed for heating the wave guide to soften the solder, it would be very difficult, to say the least, and probably impossible, to quench or cool the wave guide in such manner as to prevent material damage to the rubber-like jacket. In any event, any use of oven heating or like means would necessarily involve handling of the wave guide after heating and before quenching or cooling. Such extra handling is unnecessary with the present invention.

The heat communicated from the core 37 to the jacket 43, during the described twisting process, may cause the jacket material to throw off gas. The volume of gas thus generated, ordinarily, would be of relatively small volume; yet that which is thrown ofi at the inside of the jacket might cause a slight temporary bulging of the latter. However, upon dissipation of the heat, the gases within the jacket may to some extent re-enter the jacket material or may gradually leak away. Any remaining gases would be of relatively small volume and would not have any material effect upon the finished wave guide or its functions. Of course, if the core of the wave guide were provided with the apertures 47, the generated gas would escape inwardly through such apertures and out of the ends of the wave guide to free air. However, if such apertures are not provided in the core and if it is desired to provide a positive avenue of escape for such gas, vents or perforations 48 may be formed in the jacket of the wave guide before the latter is heated and twisted. If the finished twisted wave guide is to be used as a pressurized wave guide, the apertures 48 may be filled, after the escape of gas from the wave guide, by vulcanizing or bonding into the latter apertures a composition similar to that of which the jacket 43 is formed or some other impervious resilient composition which will form a good bond with the jacket material so that the fillings of the aperture 48 will not become dislodged.

Although the fundamental features and certain desirable supplemental features of the wave-guide twisting apparatus according to this invention have been hereinbefore described, nevertheless, certain further refinements or variations of that apparatus may be included if desired. For example, a torque spring could be associated with the handle 19 in a coaxial position relatively to the shaft 17 to impose a torque upon said handle during the passage of heating current through the core. The effect of using such a spring would be that, immediately upon softening of the solder, the torque spring would automatically turn the handle 19 angularly to give the desired twist to the wave guide, suitable means being employed, of course, tollimit the angular rotation of the plate 15 to approximately the number of degrees desired in the twist. Also, the handle 19 could be associated with electrical switch means controlling the described heating circuit that, immediately upon said handle turning to twist the wave guide, when the solder softens, the handle would operate the switch means to open the electric circuit. The handle could also be associated with suitable valve means for opening the latter to inject the com pressed air or other cooling medium into the wave guide.

Other means than those hereinbefore described can be employed for heating the solder to soften it. Thus, electric induction heating may be employed, or the apparatus may be connected by suitable ducts to a source of highly heated air for softening the solder. Regardless of what particular heating means are employed, the heat developed, preferably, should be precisely controlled so that it is transmitted to the core only sufiiciently to soften the solder.

Under certain heating conditions, the solder may have a tendency to flow inwardly, thereby leaving undesirable solder deposits on the inner surface of the wave guide and possibly tending to weaken the spiral seam of the core 37. To overcome this tendency, the apparatus may be so designed and driven, if desired, that plates 12 and 15 with a wave guide held therebetween, in its twisted condition, may be held in their twisting relationship and, while thus held, may be rotated rapidly in unison while the core is heated; the centrifugal force developed by such rotation adequately opposing any such tendency of the solder to flow inwardly.

Where a desired twisted wave guide is not required to have the described jacket, the solder at the seam need not necessarily be heated and allowed to set while the core is in its straight or untwisted form. In that situation, the straight, unjacketed wave guide may be twisted and held in its twisted form in the manner hereinbefore described, and, while it is thus held, the solder may be heated and softened for the first time and then be permitted to cool and harden to render the twist permanent.

The references herein to several possible variations of this invention have been made to afford a thorough understanding thereof without intending to limit the invention to those variations. Obviously, the present inventive concept may be utilized in various other ways than those hereinbefore described or mentioned, without departing from the invention as set forth in the following claims.

What we claim is:

l. A method of making a twisted, flexible wave guide comprising the steps of forming a conductive core by spirally winding, on a mandrel of oblong cross-section, a strip of relatively thin, flexible, electrically-conductive material, with adjacent turns of the strip in seaming engagement, and, at the same time, associating bonding material with said seam, removing said core from the mandrel, twisting said core and holding it twisted, and, while it is thus held, effecting a physical change in said bonding material to condition it to effect a bond at said seam and thereby hold the core in its twisted condition.

2. A method of making a twisted, flexible wave guide from a straight, flexible wave guide having a hollow, cross-sectionally oblong, internally unsupported conductive core of spirally wound conductive metal the turns of which are joined by a spiral, soldered seam, the said method. comprising heating the solder to soften it at the spiral seam, twisting the core and holding it twisted, and permitting the solder to cool and harden while the core is thus held. 7

3. A method of making a twisted, flexible wave guide according to claim 2, further characterized in that the wave guide is rotated rapidly about its longitudinal axis while it is thus held twisted and while the solder is soft in order to oppose inward flow of the soft solder. 4. A method of making a twisted, flexible wave guide comprising the steps of forming'a conductive core by spirally winding a strip of longitudinally-ridged, relatively thin, flexible, electrically-conductive metal, on a mandrel of oblong cross-section, with adjacent turns of the strip in seaming engagement, soldering said seam, applying a flexible jacket about the core, heating the core by means etfective interiorly of the jacket to heat and soften the solder, twisting the jacketed core while maintaining the solder in its heated, softened condition, and holding the core twisted and permitting the solder to cool and set while the core is thus held; the method further including the step of removing the conductive core from the mandrel prior to said twisting of the core.

5. A method of making a twisted, flexible wave guide comprising the steps of forming a conductive core by spirally winding a strip of longitudinally-ridged, relatively thin, flexible, electrically-conductive metal, on a mandrel of oblong cross-section, with adjacent turns of the strip in seaming engagement, applying solder to said seam, ap plying a flexible jacket about the core, heating the solder to. soften it, twisting the jacketed core while the solder is soft and holding it twisted, and permitting the solder to cool and .set while the core islreld twisted; the method further including the step of removing the conductive core from the mandrel prior to said twisting of the core. I 6. A method of making a twisted, flexible wave guide according to, claim- 5, further comprising perforating the core to permitrescape of gases from the jacket material.

7. A method of makinga twisted, flexible wave guide according to claim 6, further comprising plugging the perforations after setting of the solder to prevent further escape of fluid from within the jacket.

References Cited in the file ofvthis patent UNITED STATES PATENTS 1,536,944 Steenstrup May 5, 1925 1,550,157 Gillette -4 Aug. 18, 1925 1,677,523 Herbst July 17, 1928 1,875,483 Naylor Sept. 6, 1932 2,087,274 Anderson July 20, 1937 2,154,942 Karmazin Apr. 18, 1939 2,288,094 Karmazin June 30, 1942 2,290,338 Koehring July 21, 1942 2,293,794 Bell Aug. 25, 1942 2,338,847 Hansen Jan. 11, 1944 2,366,164 Weick Jan. 2, 1945 2,461,765 Olt Feb. 15, 1949 2,515,097 Schryber July 11, 1950 2,566,439. Beachle r Sept. 4, 1951 

